1. Field of the Invention
The invention is directed to a fuel injection valve for internal combustion engines.
2. Description of the Prior Art
A fuel injection valve of the type with which this invention is concerned is known, for example, from German Patent Disclosure DE 195 08 636, which discloses a valve body which discharges with its free end into the combustion chamber of the engine to be supplied. The valve body has an axial blind bore, originating at its end face remote from the combustion chamber, that serves as a guide bore for a pistonlike valve member that is axially displaceably guided in this guide bore. On its lower end toward the combustion chamber, this valve member has a valve sealing face, with which it cooperates with a valve seat face formed on the closed end of the guide bore. Downstream of the sealing line between the valve sealing face and the valve seat face, an injection opening in the wall of the valve body is provided, which originating at the guide bore discharges into the combustion chamber of the engine to be supplied; the passage of fuel to this injection opening is controlled by the sealing cross section between the valve seat face and valve sealing face.
On its end remote from the combustion chamber, the valve body of the known fuel injection valve is braced axially against a valve holding body via a lock nut; an intermediate disk is fastened between the end faces, facing one another, of the valve body and of the valve holding body.
The known fuel injection valve also has a pressure chamber in the valve body; the pressure chamber is formed by a cross-sectional enlargement of the guide bore, and the valve member protrudes into it with a pressure shoulder pointing in the opening direction. This pressure chamber extends as far as the valve seat face and is filled with high fuel pressure via a pressure conduit. To that end, the pressure conduit protrudes through the valve body, the intermediate disk, and the valve holding body, and can be connected to a high-pressure fuel pump via an external high-pressure inlet line. The part of the pressure conduit extending in the valve body is embodied, beginning at the end face toward the intermediate disk, as an oblique bore and intersects the pressure chamber at its radially outward-pointing end.
The known fuel injection valve has the disadvantage that a nip region, formed in the valve body between the guide bore and the oblique bore, severely impairs the high-pressure resistance of the entire fuel injection valve. In order to make this nip region more resistant to high-pressure, especially at the level of the entrance orifice of the oblique bore into the pressure chamber, the annular shoulders of the valve holding body and of the lock nut in the known fuel injection valve are already embodied as beveled in such a way that the axial fastening forces on the fuel injection valve introduce a radially inward-oriented force component into the valve body, in order to counteract enlargement of the guide bore in the nip region. However, even this provision is inadequate to significantly increase the high- pressure resistance of the valve body in the region of intersection among the oblique bore, guide bore and pressure chamber, since the wall rib region that remains between the oblique bore of the pressure conduit and the guide bore is still very small, and thus there is still the risk of breakage at this point under very high fuel injection pressures.
The fuel injection valve for internal combustion engines according to the invention, has the advantage over the prior art that the wall rib region between the oblique bore of the pressure conduit and the guide bore can be increased in size considerably, particularly in the region of the inlet opening of the oblique bore into the pressure chamber, compared with conventional fuel injection valves. This is advantageously made possible by greatly increasing the angle of inclination of the oblique bore to a longitudinal axis of the fuel injection valve, so that the angle of intersection is made considerably larger. The angle between the axis of the oblique bore and the longitudinal axis of the fuel injection valve is advantageously between 15 and 35xc2x0, and is preferably 23xc2x0.
The very much more-oblique disposition of the oblique bore in the valve body advantageously first becomes possible by a great reduction in the length of the oblique bore. This shortening of the oblique bore is made possible according to the invention by the provision of an annular shoulder on the end of the valve body remote from the combustion chamber; the resultant annular shoulder face can now be brought axially close to the pressure chamber in the valve body, so that large angles of inclination between the axis of the oblique bore and the longitudinal axis of the fuel injection valve become possible. What would be ideal here is a virtually perpendicular entrance of the oblique bore into the pressure chamber; the inclination of the oblique bore can now be varied via the axial length between the pressure chamber and the annular shoulder face. In order, despite the shortest possible length of the oblique bore, to furnish the largest possible guide area of the guide bore in the valve body for guiding the valve member, the valve body, on its end remote from the combustion chamber, has a tubular rib region that protrudes axially past the annular shoulder face, and the guide area for the valve member can be optimized by way of the length of this tubular rib region. The intermediate disk, fastened between the valve body and the valve holding body, is now adapted to the new geometry of the valve body, and it has a geometry complimentary thereto on its end toward the valve body. To that end, the intermediate disk is now advantageously cup-shaped, and on its open end toward the valve body it has a central receiving opening, into which the tubular rib region of the valve body protrudes. The intermediate disk is designed in such a way that the valve body comes to rest sealingly with its annular shoulder face on an axially protruding annular end face of the intermediate disk, yet a play remains between the end of the tubular rib and the end face on the bottom of the receiving opening. In this way, a secure sealing of the pressure conduit is assured at the connecting faces between the intermediate disk and the valve body and between the intermediate disk and valve holding body. Furthermore, it is possible to compensate for play in the length tolerances between the various components.
A further advantage of the fuel injection valve of the invention is achieved by increasing the diameter of the pressure conduit downstream toward the pressure chamber. The successive diameter regions in the valve holding body, intermediate disk and valve body each have a slightly larger diameter, so that the incoming fuel flow cannot be made turbulent by edges or cross-sectional reductions at the transitions between the various components.